Vibration rotating equipment

A more sophisticated and increasingly popular method of on-condItion maintenance is to monitor the performance of equipment on-line. For example, a piece of rotating equipment such as a turbine may be monitored for vibration and mechanical performance (speed, inlet and outlet pressure, throughput). If a base-line performance is established, then deviations from this may indicate that the turbine has a mechanical problem which will reduce its performance or lead to failure. This would be used to alert the operators that some form of repair is required. 

Uses. In architectural and industrial appHcations vibrational isolators are used to reduce transmission of vibration into building stmctures from rotating or reciprocating machinery, such as ventilating fans, pumps, chillers, industrial machinery, and the piping and ductwork coimected to this equipment (6). Vibration isolators also can be used to isolate vibration-sensitive equipment or noise-sensitive areas from sources of vibration. Examples are special pneumatic isolators to protect electron microscopes, and isolators used to support floating concrete floors in recording studios. 

Most rotating equipment includes electric motors or steam dryers that generate noise at a constant frequency. Air cooler fans are a source of noise that can be reduced by lowering the fan speed and increasing the number of blades. Pump motor noise can be reduced by including a shroud or fan cover that is accurately lined. Centrifugal compressor noise reduction can be achieved by blade design and the use of compressor pulsation noise reduction, silencers, and vibration isolation. 

Vibration is both a cause of problems and an effect of equipment problems. The potential destructive force of an out-of-balance load has led to setting lower shutdown limits on the magnitude of vibration than other rotating equipment. Flexible connections for process and utility lines become a must so these vibration problems are not transmitted to connected equipment. Flexible hoses with liners having concentric convolutions (bellows type) avoid the sharp points inherent with spiral metallic liners. By avoiding the sharp point the liner is less likely to cut the exterior covering. 

IRI 1991a. Vibration in Rotating Equipment. IRInformation Manual 6.0.8.1.0. Industrial Risk Insurers, Hartford, CT. 

The present trend in rotating equipment is toward inereasing design speeds, whieh inereases operational problems from vibration lienee the importanee of vibration analysis. A thorough appreeiation of vibration analysis will aid in the diagnoses of rotor dynamies problems. 

A total analysis of high-speed rotating equipment requires a eomplex blend of performanee and vibration data. The trend toward total analysis is growing with the problems of an energy shortage and the need for maximum plant utilization. Performanee analysis is essential in the effieient utilization of turbomaehinery and, when eoupled with vibration analysis, is an unbeatable tool as a total diagnostie system. 

Les spectres sont enregistres par im spectrographe Perkin-Elmer equipe d une optique en fluorure de lithium. Le spectrographe est rempli d air deshy drate afin d eviter les perturbations de lecture par les bandes de vibration-rotation de l eau atmospherique. Notons que la precision relative des lectures est de Fordre du cm 1 pour les bandes OH libre et de Fordre d une dizaine pour les bandes OH associees a cause de la plus grande largeur de ees dernieres bandes. 

Vibration monitor and overspeed trip on large-scale rotating equipment... 

Effective predictive maintenance programs incorporate multiple features. However, the key to rotating equipment predictive maintenance is a comprehensive vibration surveillance and analysis program. A change in a machines health or operation nearly always causes an easily detectable vibration change long before the machine fails. 

Verifying the quality of a machine overhaul. The vibration program can provide assurances that the rotating equipment has been repaired correctly and that there are no residual problems. 

Installation of heavy and/or rotating equipments which can create vibrations shall be on the ground floor as far as possible since they can fall down if the support legs get corroded in the chemical plant (which can be possible). The vibrations can weaken the structures. 

Dynamic Analysis. Dynamic Analysis (Modal Analysis) was completed to determine the fundamental natural frequencies and corresponding modal shapes of the A-frame structure. Natural frequencies were calculated to be 0.6 ( ) Hz (pin-ended) and 0.8 ( ) Hz (fixed-ended) in line with the ropes, and 0.8 ( ) Hz (pin-ended) and 1.0 ( ) (fixed-ended) perpendicular to the ropes. The natural frequencies were used to determine the wind gust load factor (Cg), examine the NBCC (2010) requirements for earthquake design, and check for possible vibrations that could be initiated by the frequency of rotating equipment corresponding the primary natural frequencies of the structure. 

SuccessM rotating equipment predictive maintenance programs require several elements. Typical elements include an portable vibration detectors, efiective lubrication program with oil analysis to detect residual metal particles, thermography, machine monitoring instramentation, repair specifications, repair history records, advanced training of mechanics, and the use of data management computers. 

Well-planned maintenance schedule routine testing of equipment for condition monitoring (e.g., vibration for rotating equipment)... 

Any piece of rotating equipment experiencing excessive vibration should be taken out of service before additional damage is done to its seals, bearings, or labyrinths. One quick way to determine the magnitude of the problem is to stand a nickel on its edge on the pump or compressor case. If the coin cannot maintain its balance, there is a good chance that vibration is too excessive to permit safe continued operation. 

One may expect rotating equipment to make odd sounds, but passive equipment such as heat exchangers should behave with greater decorum. That is possibly why noisy vibrations emanating from heat-transfer equipment are often such a mystery. Take, for example, the case of the vibrating waste-heat boiler. 

All rotating equipment has a vibration signature. These include ... 

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